. 2013 Feb 1;64(6):1485–1496. doi: 10.1093/jxb/ert005

Table 2.

Minimum fluorescence (F ₀), maximum fluorescence (F _m), variable fluorescence (F _v), and maximum photochemical efficiency of PSII (F _v/F _m) in leaf 3 and leaf 4 of an old (released in 1961) and a modern (released in 1997) winter wheat cultivar exposed to elevated CO₂ and/or O₃ for 21 d in OTCs. Control (CO₂, 385±4 ppm+CFA, 4±0.02 ppb O₃); elevated CO₂ (CO₂, 714±16 ppm+CFA, 4±0.02 ppb O₃); O₃ (ambient CO₂, 385±4 ppm+elevated O₃, 72±5 ppb O₃ for 7h d^–1, 9.00–16.00h) and elevated CO₂+O₃ (elevated CO₂, 714±16 ppm+elevated O₃, 72±5 ppb for 7h d^–1). Overall, elevated CO₂ significantly (P <0.05) increased F _m and F _v in the young leaf. Elevated CO₂ considerably (P <0.01) increased F _v/F _m in both matured and young leaves. Exposure to O₃ decreased F _m and F _v in the matured leaf, but increased F ₀, F _m, and F _v in the young leaf. High O₃ decreased F _v/F _m in the mature (P <0.001) and young (P <0.1) leaves of wheat cultivars. Results are shown as means±1 standard error (n=10). Means with the same letter were not significantly different.

Treatment	F ₀		F _m		F _v		F _v/F _m
Treatment	Leaf 3	Leaf 4	Leaf 3	Leaf 4	Leaf 3	Leaf 4	Leaf 3	Leaf 4
(a) Beijing 6 (1961)
Control	248±12^c	237±19^bc	1356±48^c	1299±88^c	1108±38^c	1062±71^c	0.82±0.00^a	0.82±0.01^ab
CO₂	246±13^c	216±21^c	1345±53^c	1236±87^c	1099±42^c	1020±73^c	0.82±0.00^a	0.82±0.01^ab
O₃	252±15^c	261±22^bc	1209±55^c	1303±97^c	957±46^d	1041±77^c	0.79±0.00^c	0.80±0.01^c
CO₂+O₃	242±14^c	277±21^bc	1246±50^c	1605±81^b	1004±44^cd	1328±74^b	0.81±0.00^ab	0.83±0.01^a
(b) Zhongmai 9 (1997)
Control	308±15^ab	291±20^ab	1713±51^a	1635±82^b	1405±41^a	1344±75^b	0.82±0.00^a	0.82±0.01^ab
CO₂	273±13^bc	263±21^bc	1509±53^b	1459±87^bc	1236±42^b	1196±77^bc	0.82±0.00^a	0.82±0.01^ab
O₃	275±17^bc	271±24^bc	1216±57^c	1384±91^bc	941±47^d	1113±78^bc	0.77±0.00^d	0.80±0.01^c
CO₂+O₃	323±12^a	347±22^a	1586±53^ab	1956±84^a	1262±42^b	1608±76^a	0.80±0.00^bc	0.82±0.01^ab